“Enforcement actions away from the border are within the jurisdiction of the U.S. Border Patrol and performed in direct support of immediate border enforcement efforts and as a means of preventing smuggling and criminal organizations from exploiting existing transportation hubs to travel to the interior of the United States,” the statement said. “These operations at transportation hubs serve as a vital component of the U.S. Border Patrol’s national security efforts.”

The incident has come to light just days after reporters were finally allowed to view a facility in Texas holding immigrant children whom the U.S. government has separated from their parents.

This is at least the second time that Border Patrol agents have harassed people attempting to ride a bus. In January, Border Patrol agents in Florida asked Greyhound passengers for the IDs and took a woman into custody.

Greyhound officials said they are following the law by letting Border Patrol agents question their passengers. But the ACLU said Greyhound has the right and responsibility to demand a warrant for Border Patrol officers to board its buses.